I was thinking of peeling then when overripe, mashing them and adding some kind of starter culture like for yoghurt (I just empty probiotic capsules to make coconut yoghurt), covering it and putting it somewhere warm overnight or for a couple of days like with yoghurt.

Pray tell. I have all of this available in my kitchen, and I have never even thought to dare make yogurt myself. I am intrigued. Do share.

Stumbled into Primal due to food allergies, and subsequent elimination of non-primal foods.